topic Re: teleconverter 1.4x iii autofocus problem in EF & RF Lenses

teleconverter 1.4x iii autofocus problem

jsfarnsw — Mon, 01 Jun 2015 20:29:43 GMT

my 100-400 ii won't autofocus with a 1.4x iii on an EOS 70D. When I install the teleconverter, the camera automatically switches from AF Servo to M Focus.

Solutions?

Re: teleconverter 1.4x iii autofocus problem

jrhoffman75 — Mon, 01 Jun 2015 20:50:34 GMT

I am pretty sure the problem is related to the fact that when you add the 1.4 teleconverter to the f/4.5 lens the max aperture becomes smaller than f/5.6.

Re: teleconverter 1.4x iii autofocus problem

jsfarnsw — Mon, 01 Jun 2015 20:58:25 GMT

that doesn't make sense, because this converter and lens are supposed to work together with AI.

Re: teleconverter 1.4x iii autofocus problem

jrhoffman75 — Mon, 01 Jun 2015 21:03:30 GMT

They will on a 1D series camera, and I believe in LiveView. But for through the lens AF the non-pro cameras have an f/5.6 limit.

See this article: http://photo.stackexchange.com/questions/16399/what-apertures-are-required-to-enable-autofocus-including-cross-type-or-high-pr

Re: teleconverter 1.4x iii autofocus problem

RobertTheFat — Mon, 01 Jun 2015 21:17:49 GMT

@jsfarnsw wrote:
my 100-400 ii won't autofocus with a 1.4x iii on an EOS 70D. When I install the teleconverter, the camera automatically switches from AF Servo to M Focus.

Solutions?

None, I think. A 70D won't autofocus at an aperture smaller than f/5.6. (A few cameras will autofocus at f/8, but the 70D is not one of them.) The teleconverter cuts the maximum aperture of your f/4.5 lens to (if my math is correct) f/6.3.

Re: teleconverter 1.4x iii autofocus problem

jsfarnsw — Mon, 01 Jun 2015 22:36:11 GMT

Thanks everyone. I did not realize the AF systems required that much light to work properly.

Re: teleconverter 1.4x iii autofocus problem

ebiggs1 — Tue, 02 Jun 2015 14:10:00 GMT

You can alway manual focus it.

Some cameras can have one or some of their contact pins disabled and the camera will AF (put tape over them). I don't know if this is true on a 70D. And I don't recommend doing it but you may search and find out for sure.

If it does work it will be very slow and not really all that accurate. Just MF it, like the good ole days!

Re: teleconverter 1.4x iii autofocus problem

amfoto1 — Tue, 02 Jun 2015 15:42:57 GMT

@jsfarnsw wrote:
Thanks everyone. I did not realize the AF systems required that much light to work properly.

AF needs adequate light to work reasonably fast and reliably.

Do an internet search about teleconverters and taping up some of the contacts. This "fools" the camera into not realizing the converter is there, so that it will still try to AF the lens. Just don't expect focus to perform very well. It will be slower and in lower light situations or with low contrast subjects it may hunt a lot and even fail to achieve focus. There's a reason Canon sets a limit and turns it off, when a lens/teleconverter combo exceeds the rated AF capabilities.

You'll have to find a website where someone illustrates which pins to tape up. I haven't done the tape trick myself... I simpy don't bother with TCs on lenses where it would exceed the light levels, or in a few cases I just manually focus (500/4 with a 2X on it, for example).

7D Mark II (not the original one), 5D Mark III (not the II or original), all 1-series (film and digital) and the EOS-3 film cameras are "f8 capable", meaning that they can still AF (mostly with one center AF point only... 5DIII can use a small group of points in the center I believe) when a lens + TC makes for an f8 or larger aperture. All other Canon cameras, including 70D are "f5.6 capable".

The 100-400mm is f4.5-5.6 already... so adding even a weaker 1.4X, makes for an f6.3-f8 combo that exceeds your camera's design capabilities. But some folks manage to make it work to a limited extent with a few small, carefully placed pieces of Scotch tape!

Note: There are a few third party lenses that are f6.3 even without any TC, yet still AF... probably by similarly "fooling" the camera.

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER

Re: teleconverter 1.4x iii autofocus problem

ebiggs1 — Tue, 02 Jun 2015 19:29:35 GMT

"Note: There are a few third party lenses that are f6.3 even without any TC, yet still AF... probably by similarly "fooling" the camera."

And you are correct. The big 150-600mm Tamron and Sigam both report f5 to the camera. Even though it is at 600mm and f6.3. I hear rumors that Canon is testing a 600mm f6.3 prime. It will interesting to see how they handle it.

Re: teleconverter 1.4x iii autofocus problem

RobertTheFat — Tue, 02 Jun 2015 20:30:16 GMT

@ebiggs1 wrote:
"Note: There are a few third party lenses that are f6.3 even without any TC, yet still AF... probably by similarly "fooling" the camera."

And you are correct. The big 150-600mm Tamron and Sigam both report f5 to the camera. Even though it is at 600mm and f6.3. I hear rumors that Canon is testing a 600mm f6.3 prime. It will interesting to see how they handle it.

Does it matter? Anyone who can afford one will already have at least one of the f/8-capable cameras. Of course any extender will throw it over the limit, but who needs an extender with a 600mm lens?

Re: teleconverter 1.4x iii autofocus problem

amfoto1 — Wed, 03 Jun 2015 04:54:41 GMT

@RobertTheFat wrote:

@ebiggs1 wrote:
"Note: There are a few third party lenses that are f6.3 even without any TC, yet still AF... probably by similarly "fooling" the camera."

And you are correct. The big 150-600mm Tamron and Sigam both report f5 to the camera. Even though it is at 600mm and f6.3. I hear rumors that Canon is testing a 600mm f6.3 prime. It will interesting to see how they handle it.
Does it matter? Anyone who can afford one will already have at least one of the f/8-capable cameras. Of course any extender will throw it over the limit, but who needs an extender with a 600mm lens?

I don't know about that... We're discussing a $2200 Canon 100-400 Mk II here.

The Sigma "C" 150-600 and Tamron 150-600mm are both very affordable for such long telephotos. Under $1100 US.

Even the Sigma "S" 150-600 isn't too bad at $2000. That's pretty close to the price of the 100-400mm being discussed here, too.

Any of those seem like bargains compared to the EF 200-400/4 with built-in, matched 1.4X ($11,000) or an EF 600/4 Mark II ($11,500).

But I agree with you... on a crop sensor camera a 600mm lens is an extremely long focal length. Adding a 1.4X to it would be sorta nuts. Shooting through a lot of atmosphere can begin to have some effects even at 600mm. Even 400mm is a whole lot of lens on an APS-C camera.

Might be better to try to get a wee bit closer to the subject, instead.

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER

Re: teleconverter 1.4x iii autofocus problem

ebiggs1 — Wed, 03 Jun 2015 12:32:12 GMT

"Might be better to try to get a wee bit closer to the subject, instead."

Of course this is always the best solution.

"I don't know about that... We're discussing a $2200 Canon 100-400 Mk II here."

You don't know about, what?

Re: teleconverter 1.4x iii autofocus problem

amfoto1 — Wed, 03 Jun 2015 13:58:49 GMT

@ebiggs1 wrote:

"I don't know about that... We're discussing a $2200 Canon 100-400 Mk II here."

You don't know about, what?

"Anyone who can afford one will already have at least one of the f/8-capable cameras..."

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER

Re: teleconverter 1.4x iii autofocus problem

ebiggs1 — Wed, 03 Jun 2015 14:31:27 GMT

Yeah, I guess, likely.

Re: teleconverter 1.4x iii autofocus problem

jsfarnsw — Wed, 03 Jun 2015 15:09:59 GMT

I stand as a case in point. I own one camera, an EOS 70D, and one lens, the 100-400mm ii. And a 1.4x iii converter.

Re: teleconverter 1.4x iii autofocus problem

RobertTheFat — Wed, 03 Jun 2015 16:22:59 GMT

@jsfarnsw wrote:
I stand as a case in point. I own one camera, an EOS 70D, and one lens, the 100-400mm ii. And a 1.4x iii converter.

Yeah, but you didn't pay $11,500 for that lens. If you had, I daresay the 70D wouldn't be your only camera.

Re: teleconverter 1.4x iii autofocus problem

ebiggs1 — Wed, 03 Jun 2015 17:58:31 GMT

???????????

Re: teleconverter 1.4x iii autofocus problem

jsfarnsw — Wed, 10 Jun 2015 03:31:31 GMT

Okay, I've tried the tape trick. True, it's slower and less sharp than the normal AF without the TC. However, it gets you close enough to manual focus from there quickly. This probably means fewer missed shots when photographing wildlife.

I'm not convinced that there's a technological reason that the 70D can't AF down to F8. The sensor may actually be better equipped to handle this than other "pro" cameras. Is Canon trying to sell "pro" camera bodies by intentionally disabling more capable "amateur" bodies?

Time for a firmware update. Shame on Canon that we have to use scotch tape to do wat they are too timid to do in firmware.

Re: teleconverter 1.4x iii autofocus problem

jrhoffman75 — Wed, 10 Jun 2015 11:04:09 GMT

There's probably some of paragraph 2 going on.

But, all the lens contact does is send the aperture value. All of what you observed in paragraph 1 would exist. That's probably not an acceptable level of performance for a autofocus camera.

The instruction manual for the 100-400 clearly states it won't autofocus with teleconverters, but gives a footnote for some cameras. You did receive the lens capability you paid for.

Re: teleconverter 1.4x iii autofocus problem

ebiggs1 — Wed, 10 Jun 2015 13:02:40 GMT

"Shame on Canon that we have to use scotch tape to do wat they are too timid to do in firmware."

How can you say that when you said ...

"... it's slower and less sharp than the normal AF without the TC."

Do you really think Canon would advertize, "Our cameras focus slower but get you close to AF so you can finish in MF!"

"Plus it's almost sharp!"

You did get what you bought. The tape is a trick to fool the camera to work under conditions it was not designed to.